黄河乌兰布和沙漠段沿岸风沙流结构与沙丘移动规律

为明确黄河乌兰布和沙漠段沿岸的风沙活动及沙丘移动特征,该文以黄河乌兰布和沙漠段沿岸的流动沙丘为研究对象,采用野外观测与实验室分析相结合的方法对沿岸沙丘的起沙风况、沙物质组成、风沙流结构及沙丘移动规律进行初步的定量研究。结果表明:起沙风的主风为西南—西风,集中于3-5月份,且5～6m/s风占起沙风的50.26%;沙物质粒径以细砂(0.1～0.25mm)为主,沿黄段沙丘粒径极细砂以下(≤0.1mm)的沙物质粒径组成比沙漠腹地减少8.92%;距地60cm高度范围内,81.75%的沙物质在0～10cm高的气层中通过。在沙丘的不同部位上,相对输沙量与高程之间有着良好的幂函数关系;沙丘向前移动的距离为8.19m/a,主要发生在3-5月份。该研究结果可为合理计算入黄风积沙量及完善黄河沿岸综合防护体系提供科学依据。     

基于无人机技术黄河沿岸沙丘移动速度监测及影响因素分析

为更便捷地监测乌兰布和沙漠黄河沿岸沙丘移动速度并解析其影响因素,该研究以乌兰布和沙漠沿黄段沙丘为研究对象,应用无人机航拍技术开展沿岸沙丘的季节性地貌过程和影响因素研究。结果表明:1)研究区沙丘年移动速率1.08～2.27 m/a,多年平均输沙势为78.82 VU,年合成输沙势为25.92 VU,处于低风能环境,8～12 m/s等级风输沙势是年输沙势的主要部分,约占73.24%。方向变率(合成输沙势(Resultant Drift Potential,RDP)与输沙势(Drift Potential,DP)的比值)RDP/DP保持在0.30～0.46之间,属于中等变率。合成输沙方向RDD为57.83°～107.39°,与沙丘移动方向较为一致,西风组占全年输沙势的52.09%,是沙丘年移动的主要驱动力。2)沙丘移动速率具有明显的季节特征,整体呈现春季移动速率快,冬末-春初次之,秋季与秋末-冬末相近,夏季移动速率最慢。其中,秋末-冬末、春季和秋季输沙势DP 8.48～20.49 VU,合成输沙势方向在90.02°～95.54°之间,RDP/DP值均在0.3～0.8之间,属于中等变率,西风组作用显著,这与年合成输沙方向及沙丘走向较为一致;冬末-春初和春末-夏季分别受东北风(NE)和南风组(SSE、S、SSW)作用,沙丘通过形态变化适应风向,移动速度降缓。季节输沙势主要集中在8～10m/s风速等级,约占整个季节输沙势的40.76%～56.93%。3)综合各季节和年际输沙势与沙丘移动距离呈线性正相关,拟合方程为y=1.02+0.006 62x(R~2=0.339,F=5.616,P=0.045),方程总体显著,输沙势可以表征该地区沙丘移动距离。基于无人机监测的沙丘运动研究综合显示,风况是该地区影响该地区沙丘移动的主要动力,其中西风组8 m/s以上风速是研究区沙丘移动的主要驱动力。风向变率和合成输沙势方向与沙丘移动方向一致时沙丘移动则快,不一致时则缓;无人机可在较大尺度上为沙丘移动提供更为便捷的监测服务,研究结果可为同类地区沙丘移动的无人机监测提供参考依据。     

库姆塔格沙漠西缘风况特征及沙丘运移规律

利用风况资料和Google Earth卫星影像，分析研究区域的风况特征及沙丘运移特征，并研究沙丘年运移速度、方向及其规律，对防沙治沙手段的提高具有重要意义。结果表明：（1）研究区年平均风速为1.535~1.768 m/s，起沙风平均风速最高值出现在5，6月，全年起沙风平均风速的最低值出现在1月。（2）起沙风和输沙势主要分布在WSW、W、WNW和NW方位。（3）输沙势为0~26 VU，属于低风能环境；风向变率为0.5~0.9，属于中风向变率，钝双峰风况。（4）研究区沙丘年平均移动速度为12.26 m/a，沙丘平均年前移值在10 m以上，属最快速类型，平均移动方向为125.13°，与当地合成输沙方向基本一致。（5）沙丘运移速度与沙丘高度、宽度呈负相关关系，除沙丘高度、宽度以外，风速、输沙势、沙丘密度也影响沙丘的运移速度。     

乌兰布和沙漠不同土地利用类型粒度特征分析

以乌兰布和沙漠段流动沙丘、沙丘前草地、沙丘前农田为研究对象,对沙丘各部位和草地、农田不同深度(0~1m)土壤粒度特征的变化规律进行了分析。结果表明:流动沙丘土壤以细砂为主,农田以粉粒为主,草地以细砂和中砂为主;随着土层深度的增加农田土壤粒径增大,草地粒径减小,沙丘无明显变化;流动沙丘粒度分布曲线为单峰,而草地和农田为双峰。农田偏度呈现近对称到极正偏态的分布趋势,分选较差;草地则呈近对称到正偏态再到极正偏态分布的趋势,分选较好到很差;沙丘分选很好,分选性差异不大。     

黄河乌兰布和沙漠段沿岸不同高度典型沙丘风沙特征

为探究乌兰布和沙漠沿黄段典型沙丘的风速流场与风沙运移特征,以3座不同高度的典型沙丘为研究对象,对沙丘不同部位5个高度的风速流场、风速廓线、风速加速率及输沙量进行了测定。结果表明:(1)风速从沙丘迎风坡脚至背风坡坡脚呈现先增大后减小再增大的"S"型趋势,沙丘顶部风速最大,背风坡中部最小。(2)沙丘各部位风速的垂直变化与高度的对数值呈V=aln(z)+b线性变化规律,风速廓线斜率a由沙丘顶部向迎风坡脚与背风坡脚逐渐增大。不同高度沙丘的摩阻流速与粗糙度变化趋势不一。(3)沙丘发育尺度对沙丘迎风坡风速加速率影响明显,其沙丘发育尺度越大,对气流的反馈作用越强,迎风坡低层20cm风速加速率明显高于高层风速加速率;(4)沙丘不同部位0~100cm的输沙率随高度呈幂函数规律递减,输沙量主要集中在0~10cm内,但不均匀,大部分集中在0~4cm,且在距地高度约4~5cm处是相对输沙量不随高程变化的不变层。     

乌兰布和沙漠沿黄段风沙土有机质和碳酸钙含量特征

土壤有机质和碳酸钙与土壤风蚀可蚀性密切相关,深刻地影响着土壤风蚀过程.以乌兰布和沙漠沿黄段风沙土为研究对象,分析不同沙丘类型和沙丘部位土壤有机质和碳酸钙的含量特征及其相互关系.研究结果显示:1)乌兰布和沙漠沿黄段流动、半固定、固定沙丘土壤有机质质量分数分别为1.71％、1.57％和2.21％,碳酸钙质量分数分别为0.1...     

塔克拉玛干沙漠风沙流定量研究

<正> 一、流动沙漠风沙流模式 塔克拉玛干沙漠中沙丘的形态很复杂,大体上可分为新月形沙丘、沙链状沙丘、穹状沙丘和金字塔形沙丘4种类型。沙丘形态是流沙移动的产物,沙丘运动实际上是风运移流沙的过程。风沙流动往往是一种整体的移动,故在研究风沙流时我们不是从单一的沙粒运动着手,而是从沙丘整体形态的运动着手进行分析的。     

乌兰布和沙漠乌海段新月形沙丘表层沉积物粒度与重金属分布特征

以乌兰布和沙漠乌海段下风向新月形沙丘为研究对象,运用样方调查与室内实验相结合的方法,对比分析新月形沙丘表层土壤及降尘中沉积物粒度特征,Mn、Cu、Zn、Cr、Fe等重金属元素及其与粒径的相关性及重金属来源,并对其潜在生态风险进行评价。结果表明:(1)沙丘不同部位粒径主要以极细砂和细砂为主,降尘主要以极细砂、粉粒为主,但上风向沙丘粒度主要以细砂和中砂为主,工业化使沙丘表面粒径细化。(2)沙丘表层及降尘中重金属含量表现为FeMnCrZnCu,Mn、Cu、Zn、Cr含量均高于背景值,且降尘中重金属含量与沙丘具有明显差异性。重金属变异系数表现为CuFeZnMnCr,Mn、Zn中等变异(15%~36%),Fe、Cu高度变异(36%);Mn、Zn、Cu、Cr发生富集,富集系数均大于1。(3)Mn、Zn、Cu与细颗粒物质含量呈明显正相关,Zn、Cu在中砂范围呈负相关,Fe均呈负相关。(4)Cu、Zn、Cr主要来源于工业污染,部分Cu、Zn来源于人们日常生活;部分Fe、Mn来源于工业污染,其余来自于地球风化。乌海段下风向新月形沙丘属于低生态风险和轻度生态危害状态,但需控制Mn、Cu、Zn、Cr含量的增加与富集。     

柴达木盆地西南缘沙丘沉积物粒度特征及其沉积环境

[目的] 研究柴达木盆地西南缘沙丘沉积物粒度特征及其沉积环境,为格(尔木)库(尔勒)铁路防沙和安全运行提供基础数据支撑。[方法] 通过粒度分析方法对柴达木盆地西南缘沙丘区沙丘沉积物的粒度特征及沉积环境进行分析。[结果] 柴达木盆地柴西南沙区沙丘表层沉积物以细沙为主,中沙次之,平均粒径-0.14~3.49Φ,平均值为2.02Φ;分选系数为0.32～1.59,平均值为0.69,以分选较好和好的沙粒为主;偏度主要为近对称分布;峰度以中等峰态占优。自然频率分布曲线呈单峰和双峰分布模式,累积频率曲线图式为一段式、二段式、三段式。平均粒径与分选系数呈线性相关关系,即随平均粒径变细,分选逐渐变好。当峰度＜0.9时,平均粒径与峰度呈负相关;当峰度＞0.9时呈正相关。[结论] 柴达木盆地西南沙区西北部为风成环境,以风成沙为主;而东南部以湖相和河流冲—洪积环境为主,沙物质受到风力和流水的交互作用。     

乌兰布和沙漠沿黄河区域下垫面特征及风沙活动观测

为明确乌兰布和沙漠沿黄河区域下垫面特征与风沙活动特点,该文对该地区的沙丘形态、粒度特征、风速、输沙率与风沙流结构及其相互关系进行了野外调查与室内分析。结果表明:研究区横向沙丘平均宽-高比约为12.75。沙丘表面平均粒径与分选系数呈现出由丘间地至落沙坡逐渐减小的趋势,偏度则呈现出增大趋势。沙丘各部位粒度累计分布曲线均为正偏、单峰态分布。在净风与起沙风环境下,仅丘间地与沙丘顶部风速廓线呈对数形式分布;迎风坡坡脚处风速廓线多呈幂函数分布;落沙坡与背风坡坡脚处风速廓线分布形式不统一。无论在高风能环境下还是低风能环境下,从丘间地至背风坡坡脚,沙丘断面近地表风速呈减小(至迎风坡坡脚),增大(迎风坡坡脚至丘顶),再减小(丘顶至落沙坡),再增大(落沙坡至背风坡坡脚)趋势。沙丘顶部是风沙活动最为强烈的部位,沙丘各部位90%以上的输沙量集中到10cm高度以下;沙丘各部位的风沙流结构均服从三次函数分布。最后,该文针对该区域下垫面与风沙活动的特点和危害,提出相应的防治对策,以期对该区域风沙危害的防治提供参考。     

“绿色革命”以来大气CO2浓度升高对C3作物营养品质的影响

自20世纪60年代"绿色革命"以来,育种技术和农耕技术的发展促进了农作物产量的大幅提升,然而作物的营养品质出现下降趋势。在相似的遗传背景下,大气CO_2浓度升高会使单位体积农作物产品的营养元素含量下降,因此"绿色革命"至今,农作物产品的营养元素下降可能受大气CO_2浓度升高影响。通过植物生长箱模拟"绿色革命"初期和目前的大气CO_2浓度水平(310μmol/mol和400μmol/mol),针对主要C_3作物水稻、小麦和大豆,研究"绿色革命"以来大气CO_2浓度升高对其籽粒的C、N、Fe、Zn元素含量的影响,结果表明:CO_2浓度升高对3种作物籽粒的C元素含量几乎没有影响,变化幅度在±1.5%之间;籽粒的N、Fe、Zn元素含量普遍呈现下降趋势,但均未达到显著水平。     

Potential of wild species for genetic enhancement of some semi-arid food crops

Discovery and incorporation of genes from wild species provide means to sustain crop improvement, particularly when levels of resistance in the cultigens are low and virulent strains of pests and pathogens overcome the host plant resistance. The extent of utilization and the potential of the wild genepool for genetic enhancement were reviewed in five important food crops viz. sorghum, pearl millet, chickpea, pigeonpea and groundnut grown in the semi-arid tropics. Introgression from compatible wild germplasm in the primary gene pool resulted in transfer of new cytoplasmic male sterility systems in pearl millet and pigeonpea, development of high protein, cleistogamous flower and dwarf pigeonpea lines and foliar disease resistant groundnut cultivars. Utilization of wild species in secondary and tertiary gene pools has been generally limited due to sterility, restricted recombination or cross incompatibility. Nevertheless, these species are extremely important as they contain high levels of resistance to several important biotic and abiotic stresses. Several of them, like those belonging to the Parasorghum section and the rhizomatous Arachis species are sources of multiple resistances and hold great promise to sustain crop productivity.     

Faculty positions:Center for Agricultural Resources Research,Chinese Academy of Sciences

正The Center for Agricultural Resources Research(CARR),the Institute of Genetics and Developmental Biology(IGDB),Chinese Academy of Sciences,invites applicants for several research group leader positions.CARR is one of the research organizations in Chinese Academy of Sciences(CAS).We seek nominations and applications     

Soil-profile distribution of primary and secondary plant-available nutrients under conventional and no tillage

Nutrient distributions under no tillage (NT) compared with conventional disk-and-bed tillage (CT) management in the warm, humid region of the southeastern USA need to be assessed so that future placement, quantity, and type of fertilizers can be altered, if necessary, to efficiently match crop demands. We determined soil-profile distributions of pH, N, P, S, K, Ca, Mg, Na, Zn, Fe, Mn, and Cu to a depth of 0.9 m at the end of 8.5 years of continuous CT and NT management on a Weswood silty clay loam (fine, mixed, thermic Fluventic Ustochrept) in southcentral Texas. Most dramatic changes occurred within the 0–0.05 m depth, where soil under NT had lower pH, Fe, and Cu than under CT, but greater P, K, Zn, and Mn. Greater P and K under NT than under CT also occurred below the till-zone (0.15–0.3 m). At a depth of 0–0.3 m, soil under NT contained greater amounts of extractable P, K, Zn, Fe, Mn, and Cu than under CT. Nitrogen fertilization had little effect on nutrient distributions, except resulting in greater extractable K at 0–0.05 m and greater nitrate at 0–0.15 m. Few changes in soil-profile distributions were observed for extractable S, Ca, Mg, and Na. Long-term continuous use of NT on this fine-textured, high-fertility (except for N) soil had no apparent adverse effects on nutrient distributions relative to CT, but enhanced conservation and availability of P, K, Zn, Fe, Mn, and Cu near the soil surface where crop roots proliferate.     

Assessing the effectiveness of conservation measures: Resolving the “wicked” problem of the Steller sea lion

“Wicked” problems are those that are complex and that change when solutions are applied. Many conflicts in conservation fall into this category. The study approached the problem of how to constrain the apparent wickedness of a problem in the conservation management of a species by using simple empirical indicators to carry out iterative assessment of the risk to a population and to document how this risk evolves in relation to the addition of new data and the implementation of management actions. Effects of high levels of uncertainty within data and also concerning population structure were examined through stochastic simulation and by exploration of scenarios. Historical trends in the example used, the Steller sea lion, showed rapid declines in abundance in some regions during the 1980s. The current total population is 130,000-150,000 Steller sea lions through Alaska and British Columbia and this number has been stable since about 1990 in spite of regional differences in population dynamics. Regional differences in the sequence of changes in the number of pups and non-pups, suggested that an internal re-distribution of juveniles could have happened between 1980 and 1990. Current productivity also appears close to the long-term mean. Stochastic population projection using various scenarios showed that, based upon this history, the risk of extinction for the population has declined and is below reasonable thresholds for considering the population to be endangered. The trends in risk suggest that management actions taken since 1990 have probably been effective. Consequently, the conservation management objectives for the Steller sea lion are probably being met. The approach provides a mechanism, based upon experience and scenario analysis, for exploring future policy options and may help to constrain the debate amongst stakeholders about the cost-benefit trade-offs associated with different options.     

Collection and preliminary evaluation of native turfgrass accessions in Italy

Despite a raising interest on turfs in Italy, all theavailable varieties of this kind in the Country are of foreign origin, and areoften poorly adapted to the prevailing climatic conditions. This prompted tobegin a collection activity of indigenous turfgrass species, with the ultimategoal of identifying promising materials for future breeding based on localgenetic resources. The collection was carried out in three areas of Italy, viz.the northern Po Plain, the coastal region of Liguria, and the island of Sardiniathat are characterised, respectively, by subcontinental, warm temperate, andtypical Mediterranean climate. Altogether, 141 sites were visited, yielding 226accessions belonging to eight species of potential interest for turfs:Poa pratensis, Poa trivialis,Festuca rubra, Festuca arundinacea,Lolium perenne, Agrostis stolonifera,Agrostis tenuis, and Cynodon dactylon,this last being a warm-season grass. Poa pratensis andCynodon dactylon were mostly collected in northern Italyand Sardinia, respectively, whereas Festuca arundinacea andLolium perenne were rather ubiquitous. The collection sitesranged from 0 to 1040 m asl, but sites over 750 m wereonly visited in the inner part of Sardinia. All the accessions, collected aswhole plants, were transplanted at Lodi, northern Italy, where they are beingevaluated. Their preliminary evaluation for traits of importance for turf use,such as sward colour and overall quality, highlighted the great variation andthe occurrence of interesting accessions in all species. Other characters wererecorded, bearing specific importance in individual species, and in all casespromising accessions were identified. The germplasm of Festucarubra, Festuca arundinacea, and Loliumperenne proved highly infected by endophytic (symbiotic) fungi of thegenus Neotyphodium.     

Enhanced establishment and growth of giant cardon cactus in an eroded field in the Sonoran Desert using native legume trees as nurse plants aided by plant growth-promoting microorganisms and compost

To evaluate the feasibility of long-term desert reforestation technology of mixed vegetation, cardon cactus (Pachycereus pringlei) seedlings from indoor and outdoor nurseries were planted in the field adjacent to one seedling of potential legume nurse trees: mesquite amargo (Prosopis articulata), yellow palo verde (Parkinsonia microphylla), and blue palo verde (Parkinsonia florida). Some of the planting holes were also supplemented with common dairy compost. Additionally, the combinations of legume tree–cactus were inoculated with either a consortium of desert arbuscular mycorrhizal (AM) fungi, plant growth promoting bacteria (PGPB; the diazotroph Azospirillum brasilense Cd, and the phosphate solubilizer Paenibacillus sp.), or a mixture of all. The field experiments were evaluated periodically during 30 months for survival and growth. Cardons reared in an outdoor screen house survived better in the field than those reared in a controlled growth chamber and hardened later outdoors. Association with any legume nurse tree increased survival and enhanced growth of untreated cardons. For cardons growing alone, application of either compost, AM fungi, and all the treatments combined increased survival. For these plants, no treatment affected plant growth during the first 3 months after transplanting. Later, all treatments, except for AM fungi, enhanced plant growth. However, only 2 years after transplanting the enhanced growth effect of AM fungi was also significant. In the presence of the legume nurse trees, transient positive effects on cardon growth were recorded. General evaluation after 30 months of cultivation showed that the treatments positively affected cardon growth when growing alone or in combination only with mesquite amargo but not with the other two legume trees. This study proposes that young legume trees have the capacity to enhance survival and growth of cardon cactus, depending on the legume cactus combination. Additional treatments such as compost or PGPB can either amplify the effect or else attenuate it.     

Karyotypic and genome size variation in Cajanus cajan (L.) Millsp. (pigeonpea) and some wild relatives

Detailed karyotypes and 4C DNA amounts have been studied in five cultivars of Cajanus cajan and 20 species belonging to Cajanus, Rhynchosia, Dunbaria, Flemingia and Paracalyx. C. cajan shows intraspecific variability and its karyotype is most similar to that of C. cajanifolius (sect. Cajanus) in the morphology and number of satellite chromosomes and the lack of any correlation between chromosome size within the complement and asymmetry. Karyotypes of C. lineatus and C. sericeus belonging to sect. Atylia are similar with respect to maximum r-index and the ratio of longest and shortest chromosomes in their respective complements. C. acutifolius (sect. Frutocosa) is distinct in having a very low ratio (1.44) between the longest and the shortest chromosomes, while in C. albicans, C. goensis, C. scarabaeoides (sect. Cantharospermum) there is no chromosome pair with r-index >2.0. C. mollis and C. volubilis (sect. Volubilis) show similarity with regard to ratio between the longest and the shortest chromosomes and a distinct chromosome pair with an arm ratio of 2.7 and C. platycarpus is distinct (sect. Rhynchosoides) in having the smallest ratio (1.36) between the longest and the shortest chromosomes. 4C DNA amounts in Cajanus and Rhynchosia vary between 3.28 pg to 11.69 pg and 4.92 pg to 11.13 pg respectively, while in Dunbaria, Flemingia and Paracalyx these vary between 4.70 and 7:06 pg. In the genus Cajanus karyotypic features and 4C DNA amounts agree with the sectional classification and bring out a close relationship between C. cajan and C. cajanifolius. This is supported by studies based on seed protein patterns, isozyme analysis, trypsin and chymotrypsin inhibitor patterns, RFLP and RAPD data and crossability relationships. A clear relation between DNA amount and abnormalities effecting the extent of pairing and recombination in interspecific hybrids shows the importance of this study in developing future breeding programme involving C. cajan and its wild relatives that are of potential value.     

Effect of some fungicide seed treatments on the survival of Bradyrhizobium japonicum and on the nodulation and yield of soybean [Glycine max. (L) Merr.]

Several commercial fungicide seed treatments were evaluated for their possible effect on the survival of Bradyrhizobium japonicum on seeds and on the nodulation and yield of soybeans in a greenhouse and a field experiment. quinolate Pro (carbendazim and oxine copper), Vitavax 200FF (carboxin and thiram), and Monceren (pencycuron) had a small effect or no effect on the survival of B. japonicum and on the nodulation and yield of soybeans. They can thus be considered compatible with soybean seed inoculation. Germipro UFB (carbendazim and iprodione), Apron 35J (metalaxyl), and Tachigaren (hymexazol) decreased B. japonicum survival and the nodulation and yield of soybeans and thus cannot be considered compatible with soybean seed inoculation.     

Leaf position and genotype differences for mineral element concentrations in sorghum grown on tropical acid soil 1

Mineral element deficiencies and toxicities are common problems associated with sorghum [Sorghum bicolor (L.) Moench] production on acid soils. To better understand some of the mineral element problems and the analysis of plant tissue of sorghum plants grown on acid soils, four sorghum genotypes were grown on an acid Oxisol at Carimagua, Colombia limed with dolomite at 2 and 6 Mg ha^‐1.

Samples for mineral element analyses were obtained from leaves at different positions on the four genotypes. Concentrations of P and Mg were highest in the flag leaf (Leaf No. 1) and decreased as the position on the plant declined from the top of the plant for plants grown at 2 Mg lime ha^‐1. Similar decreases in P, Mg, K, and Zn concentrations occurred in plants grown with 6 Mg lime ha^‐1. Concentrations of Ca, S, Si, Mn, Fe, Cu, and Al increased as leaf position declined from the flag leaf for plants grown at 2 and 6 Mg lime ha^‐1. The higher lime supply enhanced Ca and reduced Mn and Fe concentrations in leaves. Differences in mineral element concentrations for the four genotypes used were fairly extensive. The elements to show the greatest range among genotypes were Al and Si and the elements to show the least range among genotypes were P, K, and S. Care should be used in collecting leaf samples for plant analysis and genotypic differences for accumulation of mineral elements should be considered in interpretation of results.